1. Field of the Invention
The invention relates generally to a sealing device or closure for a container, and more particularly, to a sealing device having a releasable lock.
2. Background
Containers such as test tubes have been used for many years to store sample materials such as liquids. There is often a need to seal the open end of a test tube with a removable cap to prevent contamination or loss of the sample while allowing for subsequent re-access to the sample. Also, when material has been placed in test tubes, it is sometimes necessary to remove from or add to the material without removing the cap. This can be done by using a syringe to puncture the cap. However, some caps are difficult to puncture because of their wall thickness. After a typical container cap is punctured with a syringe, the punctured cap cannot reseal the container.
A typical removable cap relies on a frictional fit between the cap and the inside surface of the test tube to seal the test tube and to retain the cap. Sometimes the cap and test tube are molded together from a plastic material, with the cap attached to the test tube by a hinge. There are disadvantages to frictional cap seals. If the test tube is dropped, the cap has a tendency to pop off, thus spilling or contaminating the sample. Heating and cooling cycles can loosen the cap, allowing it to come off the test tube. Evaporation of a sample will often occur unless the cap makes a hermetic seal with the test tube. The seal and the retention of a friction fit cap can be heightened by increasing the friction fit between the cap and test tube. However, increasing the friction between cap and container makes installation and removal of a cap much more difficult. Such difficulty can cause user fatigue when the user must cap or uncap many test tubes. Furthermore, it may be costly to achieve a precise friction fit due to tight dimensional constraints required for the inside surface of the tube and the outside surface of the cap.